Oral neoplasia and surgery (Proceedings)
The oropharynx is the fourth most common site for malignant neoplasia.
The oropharynx is the fourth most common site for malignant neoplasia. In the dog the four most common tumors seen are: epulides, malignant melanoma (MM), squamous cell carcinoma (SCC) and fibrosarcoma(FSC). These four tumors account for 80% of all oral neoplasia in dogs. Seventy percent (70%) of all neoplasia in the cat is due to squamous cell carcinoma (SCC). The most common tumor of the dental laminar epithelium is the ameloblastoma.
Or tumors can arise from cellular components of developing tooth structure. Some common and not so common lesions that originate from tooth structure are:
The epulis is the most common benign mass seen in the oral cavity of the dog. The odontogenic origin is the periodontal ligament (PDL). The current standard nomenclature for epulides is:
- fibrous - benign and respond well to excision with removal of the PDL .
- osseous - benign, more difficult to remove but responds well to complete excision.
- acanthomatous - locally invasive and need to have wide margins for successful surgical removal. Remove at least on tooth on each side of the mass.
- giant cell - similar histopathologically to acanthomatous but less aggressive.
This oral mass develops from ectodermal tissue and is usually the result of an accumulation of components of a developing tooth follicle where the tooth has failed to erupt. A failure of a tooth to erupt is termed an embedded or impacted tooth. If the crown is covered with soft tissue but not bone, it is called an embedded tooth. If a tooth in maloriented and completely in covered by or in contact with bone or other tooth structure and has failed to erupt, it is termed an impacted tooth. When surgically treating a dentigerous cyst, it is important to radiographically identify the unerupted tooth, remove it and debride the debris from the cyst wall.
Other odontogenic cysts or tumors
The other cysts included are the eruption cysts, PDL cysts, primordial cysts and gingival cysts. Ameloblastoma, ameloblastic carcinoma, squamous odontogenic and benign epithelial tumors are the other solid masses included in this group.
A neoplasia of mixed (ectoderm and mesoderm) origin. The two classifications are complex and compound. The complex odontoma is a disorganized mass that contains no recognizable tooth structure. The compound odontoma develops numerous tooth like structures call denticles.
Malignant melanoma (MM)
The most common oral malignant tumor of the dog and the least common in the cat. The most common location is the gingiva with the appearance often pigmented, roughened and/or an ulcerated surface. In the dog there is a 4:1 sex distribution of male:female. Older dogs are most commonly affected, the tumor metastasize(mets) to regional lymph nodes and distant sites readily. Usually by the time a diagnosis is made, metastatic disease is present resulting in a grave prognosis regardless of treatment. Research is currently ongoing to develop better chemical and immunotherapy.
Squamous cell carcinoma (SCC)
The second most common oral malignancy in the dog and the most common in
the cat. The most common location is the gingiva but lingual occurrence is increasing in the cat. The mass is usually erythematous, with a roughened or ulcerated surface and bleeds easily. The SCC affects middle to older aged dogs and is represented in three types: tonsillar, nontonsillar and papillary. The tonsillar form is very aggressive and mets early, the nontonsillar is less aggressive and mets later while the papillary SCC rarely mets. Prognosis obviously is directly related to metastatic potential. A fair prognosis can be given for the nontonsillar SCC that is diagnosed early and treated with aggressive surgery. The more rostral the mass, the better the prognosis. Reports have indicated that postsurgical radiation therapy improves the prognosis. A good prognosis can usually be given for a papillary SCC treated in the same manner.
The FSC is the third most common malignancy of the dog and the second in the cat. In the dog there is a 2:1 sex predilection of male:female, middle age is the most common time of occurrence. The location is often at the level of palatal maxillary PM4 with a smooth red to blue surface. The lesion mets slowly and, therefore, has a fair prognosis with aggressive surgical treatment. Postsurgical radiation treatment can also improve the prognosis for this condition.
History and clinical signs of oral neoplasia
Animals with oropharyngeal neoplasms are presented to veterinarians because of excessive salivation, bleeding from the mouth, difficulty in mastication, dysphagia, halitosis or an obvious oral mass. In some cases the mass is not obvious as in feline glossal or sublingual SCC, however, the regional lymph nodes may be enlarged.
A cough may be part of the signalment due to pulmonary metastasis. Cachexia may be present due to anorexia from mechanical interference with mastication. Generally, oral neoplasia is a disease of older dogs and cats. Exceptions would include oral viral papillomatosis and inductive fibroameloblastoma. Breeds of dogs most affected by oral tumors are:
Golden Retriever, German shorthair pointer, Weimaraner, Saint Bernard, and Cocker Spaniel.
Diagnosis and treatment of oral neoplasia
It is important to obtain a diagnostic incisional or aspirate biopsy without careless "seeding" of the disease to surrounding tissue. Generally, when an oral mass lends itself to full and complete excision initially, that is the safest and most efficient method of diagnosing and treating the tumor. If malignancy is highly suspected or has previously been documented, the submandibular lymph node(s) should be biopsied. The "en bloc" mass should be sent for histopathological evaluation to determine: 1.) malignancy, 2.) cell type and 3.) border clarity. There are times when the mass is large or located such that complete excision is unlikely without radical surgery. Once the tumor information has been gathered, a logical treatment plan can be discussed with the client.
Cryosurgery and electrosurgery have not been successful to date in complete and lasting remission of oral tumors in general. Hyperthermia and radiation therapy have shown promise in treating some oral neoplasia. Rapid improvements are occurring in veterinary oncology. When a malignant oral mass is diagnosed, it is prudent to contact a veterinary oncologist in the area and discuss staging and treatment of the disease.
Many of our patients in veterinary dentistry are older or have compromised core body functions. It is important to choose an anesthetic regimen that will provide these animals with the least risk and offer adequate analgesia intraoperatively and postoperatively. Regional anesthesia is an excellent adjunct to general inhalation anesthesia because it will:
1. allow the anesthetist to reduce systemic anesthesia levels (and risks) while providing
2. appropriate analgesia.
3. act to create vasoconstriction (lidocaine) which will enhance hemostasis.
4. combine with other drugs to aid in hemostasis and prolong analgesia (dilute
5. epinephrine 1:100,000). Caution in hyperthyroidism or cardiac disease.
6. provide long lasting postoperative analgesia (bupivicaine).
7. dramatically decrease the cost of inhalant anesthesia.
Technique and dosage (See lecture regional anesthesia and pain management)
Healing of oral surgery is similar to wound healing elsewhere in the body. However, there are modifying factors within the oral cavity that affect healing. The following factors all play a role in the healing process: the unique biochemical and anatomical function of the bones of the face and jaw; the protruding teeth; specialized tissue such as the gingiva; the constant exposure to contamination; and the specialized medium of saliva, food, and foreign material. Although these factors might retard healing in other areas of the body, healing in the oral cavity usually progresses rapidly, the major reason being the abundant vascular supply.
Before attempting to perform oral surgery, it is important to have complete command of the oral anatomy. Some common principles that are critical in the success of oral surgery are: 1.) gingiva does not have elasticity but mucosa is very elastic, therefore it is important in planning oral surgery to extend the incisions beyond the mucogingival line to take advantage of elasticity for tension-free wound closure; 2.) create incision lines with rounded corners to avoid avascularity; 3.) allow for deep tissue "bites" when suturing oral tissue; 4.) avoid tension on the suture line; 5.) plan the incision so closure of soft tissue is not over a boney void; 6.) use suture needles that do not cut or tear the tissue; 7.) use surgical technique to prevent cutting of soft tissue during closure by "suture drag; 8.) when suturing in the oral cavity always try to begin with the unattached tissue and advance toward the attached tissue. Wound healing for most healthy oral soft tissue will occur within 5 to 7 days. The suture of choice for healthy oral soft tissue is chromic gut in a 5/0 to 3/0 size when suture removal is to be avoided. Maxon, Vicryl or Dexon will require 2 to 3 weeks to absorb in the mouth and is the suture of choice when delayed healing is anticipated. The most common suture pattern used is a simple interrupted pattern, but a vertical mattress is a good pattern when extra tissue holding strength is required. Nonabsorbable sutures may be used intraorally but often require patient sedation or anesthesia for removal.
Simple flap design
Simple flaps are usually used for single tooth surgical extractions, gingival repositioning, surgical endodontics or small mass excisions. The flap configuration includes a horizontal incision with a single or double vertical releasing incision. In the case of surgical endodontic exposure, the releasing incision arms of the flap may join the horizontal incision to form a U or C shape. The vertical releasing incision gives the flap elasticity from the mucosa, therefore, any flap that requires transposition must have a vertical release into the mucosa. If boney voids will be created with extraction or en bloc removal of a mass, the flap should be planned so the closure of the soft tissue is not suspended over the bony void but instead is supporting the incision.
Double flap design
The double flap is often used to correct palatal defects. A common use for double flap is the correction an oronasal fistula. A segment of palate is inverted and sutured to a rim of buccal gingiva adjacent to the fistula. The buccal gingiva dorsal to the rim of gingiva is released by a double vertical incision beyond the mucogingival line and well into the mucosa. The vertical incisions are usually slightly divergent. The flap is undermined with a periosteal elevator until it has gained elasticity to allow coverage of the fistula and the palatal defect produced by the first flap. The double flap technique is usually reserved for oronasal fistula that have had previous closure failures.
Repositioning flap design
Repositioned flaps are often used to treat periodontal disease or increase crown length. Flaps can be constructed to be simply replaced back at the original attachment or positioned in a more coronal or apical position. Flaps that are simply replaced are often used to access deep periodontal pockets, debride diseased gingiva and prepare a gingival margin with healthy tissue. One commonly used periodontal technique employed for this is ENAP(excised new attachment procedure). Apically repositioned flaps are used to expose more root for crown lengthening or to reduce a void created by a subgingival slab fracture. The flap is made and horizontal margin is elevated to the mucosa. The area is treated and the flap is repositioned in an apical direction. Coronally repositioned flaps are prepared in a similar method but are repositioned, due to the elasticity of the mucosa, more coronally on the tooth. These flaps are often used in the treatment of furcation exposures. It is important that the vertical releasing incisions for repositioned flaps be perfectly parallel to prevent voids from occurring during closure.
When removing a portion or total segment of jaw, it is important to know the vascular anatomy and plan the surgery by preemptive ligation to avoid severe blood loss. Whenever uncontrollable hemorrhage occurs, it is important to (remember and) be prepared to ligate the carotid artery. The ligation can be temporary(Satinsky forceps or bulldog apparatus) or permanent using a crushing forceps and ligature. With proper planning and good knowledge of the anatomy, carotid artery ligation is usually not needed. Osteotomy can be performed with air driven power saws or the bone may be scored with a cross cut bur on a highspeed handpiece and the transection completed with osteotomes. Gigli wires can be used, but I find them more cumbersome and traumatic to the soft tissue. When performing a rostral maxillectomy or mandibulectomy it is usually easiest to begin the osteotomy at the midline, then begin the sectioning of the distal segment. Just before the boney segment is completely transected, an assistant can apply digital pressure to the carotid artery and prepare to clamp the maxillary (or inferior mandibuloalveolar) artery just as the segment of bone is separated from it's origin. Once the bone has been removed, it is important to insure that all sharp edges of bone have been smoothed or rounded with a ronguer or bur. Electrosurgery is useful for cauterizing small vessels but care should be taken to avoid devitalization of the tissue. Suction makes these procedures go much more smoothly. Soft tissue resection and closure should be planned to give the best function and cosmetic appearance.